1920] AGRICULTURAL BOTANY. 29 



younger branches. The early translocation of potassium is limited, occurring 

 mainly from older parts than those supplying phosphorus and nitrogen. 



Report of the department of chemistry, T. O. Smith (New Hampshire 

 Sta. Bui. 192 {1919), pp. 20-22). — A brief report is made of cooperative work 

 on the physiology of the apple, which is noted above, and an account given of 

 studies of the relation of potassium to the growth of cereals. Wheat, corn, 

 and buckwheat were grown in water and sand cultures, and it was found 

 that all three species required a supply of potassium in addition to that stored 

 in the seed itself within a few days after germination. 



Induced changes in reserve materials in evergreen herbaceous leaves, 

 O. M. TuTTLE {Ann. Bot. [London], 33 {1919), No. 130, pp. 201-210, figs. 7).— 

 The author has made a study of reserves, alterations therein, and related 

 occurrences, mainly in Linncca horealis. 



It is stated that in northwest Canada most evergreen plants are free from 

 starch as early as October, when they are found to contain a considerable 

 amount of oil. Exposure of Linnpea to higher temperature induces in darlmess 

 formation of starch, which is present in about two days, increasing until alKmt 

 the eighth day. The starch is in a highly divided state, the individual grains 

 exhibiting Brownian movement. Conversion occurs in all liealthy leaves., Low 

 temperatures are dangerous to leaves filled with starcli. The starch disappears 

 after exposure for eight days to moderately low temperatures. Starch form-a- 

 tion is associated with loss of oil content. Enzyms are present in material 

 undergoing conversation. Lipase has also been demonstrated in such materials. 

 Oxidases are present in the leaf of Linn?ea even at low temperatures. 



The compound interest law and plant growth, V. H. Blackman {Ann. 

 Bot. [London], 33 {1919), No. 131, pp. 353-360) .—The author attempts to formu- 

 late in connection with plant growth conditions what has been called the com- 

 pound-interest law. This is here claimed to be expressed approximately by the 



W 

 formulas Wi=Woe'"' or logarithm c ^^=rt, where Wo is the initial weight, 



Wi the final weight, r the rate, t the time, and e the base of natural logarithms. 

 Seed weight, rate of increase, and time period are the basic factors. These are 

 discussed in their relations. 



The efficiency index, wliich appears from the data of early workers to be 

 highest In the early stages of growth, afterward falling slightly, is claimed by 

 the author to show, in studies on Helianthus, Cannabis, and Nicotiana, a shari) 

 fall at the beginning of the reproductive period when the inflorescence first 

 appears. 



There is evidence that annual plants at the end of their period of growth may 

 lose considerably in dry weight. 



Seventeenth report of the Woburn Experimental Fruit Farm, S. U. 

 Pickering {Wohurn E.vpt. Fruit Farm Rpt., 11 {1920), pp. 89+315-325, pi. 1, 

 figs. 3). — Previous issues of this report have been noted (E. S. II., 38, p. 540), 

 as has also an explanation of the change in status of the institution (E. S. R., 

 42, p. 104). 



The main substance of the work herein reported is concerned with soil 

 water, drainage, and the toxic action of plants on each other, being a con- 

 tinuation and in part a repetition of studies previously noted (E. S. R., 26, 

 p. 639). The work is reported and discussed in considerable detail as carried 

 out with different plants, the grass employed being Festuca pratensis. It is 

 claimed that the toxic action is practically the same whether the grass is 

 grown in earth or sand and that it is not affected by the thoroughness with 

 which the grass roots are separated from the tree roots. 



